Supplemental signaling system for special railway vehicles



H. A. THOMPSON SUPPLEMENTAL SIGNALING SYSTEM FOR SPECIAL. RAILWAY VEHICLES Nov. 11, 1952 5 Sheets-Sheet 1 Filed Sept. 25, 1948 INVENTOR.

.' Thompson 1115' ATTORNEY Nov. 11, 1952 H. A. THOMPSON 2,617,922

SUPPLEMENTAL SIGNALING SYSTEM 2 2 FOR SPECIAL RAILWAY VEHICLES Filed Sept. 25. 1948 5 Sheets-Sheet 2 Fig: 1B.

- INVENTOR.

Howard A flwmpson BY 1 HIS ATTORNEY Nov. 11, 1952 H. A. THOMPSON SUPPLEMENTAL SIGNALING SYSTEM FOR SPECIAL RAILWAY VEHICLES 5 Sheets-Sheet ,3

Filed Sept. 25, 1948 A T m A m m H aw H. A. THOMPSON. SUPPLEMENTAL SIGNALING SYSTEM FOR SPECIAL RAILWAY VEHICLES Nov. 11, 1952 5 Sheets-Sheet 4 Filed Sept. 25, 1948 INVENTOR.

Howard A. flmmpson BY M 111s ATTORNEY r v Nov. 11, 1952 H. A. THOMPSON 2,617,922

SUPPLEMENTAL SIGNALING SYSTEM FOR SPECIAL RAILWAY VEHICLES -5 Sheets-Sheet 5 Filed Sept. 25, 1948 INVENTOR. Howard Thompson BY W HIS A 7"1 'OENEY Patented Nov. 11, 1952 SUPPLEMENTAL SIGNALING SYSTEM FOR SPECIAL RAILWAY VEHICLES Howard A. Thompson, Edgewood, Pa., assignor to Westinghouse Air Brake Company, a corporation of. Pennsylvania Application September 25, 1948, Serial No. 51,276

7 Claims.

My invention relates to railway signaling systems, and particularly to supplemental signa ing systems for governing the movement of special railway vehicles which move independently of the usual block signal systems.

Special railway vehicles, such as small motor cars used by maintenance men, are usually equipped with. insulated wheels or axles so that these cars will not shunt the track circuits of signaling systems which govern train movements. As a result, the conventional railway signaling systems do not protect the operator of a motor car or other special vehicle of that character.

An object of the present invention is to provide an improved supplementary signaling system for indicating to operators of special vehicles of the type designed that a train is approaching.

Another object is to provide an improved supplementary signaling system for the continuous control of moving vehicles of a special character which may be superimposed without interference upon a conventional cab signaling or train control system for the continuous inductive control of standard railway vehicles.

The supplemental signaling system of my invention is an improvement upon those described in the copending applications for Letters Patent of the United States, Serial No. 996, filed January 7, 1948, and Serial No. 5,138, filed January 29, 1948, by Wilbut V. Grosjean, both of which are entitled Supplemental Signaling Systems for Special Railway Vehicles. The improvements provided by my invention comprise the provision V of means for selectively suplying motor car indicator control energy or cab signaling energy to each of the sections of a stretch of railway track in response to trafiic conditions, and the provision of means for selectively changing the character of the motor car indicator control energy to thereby indicate the direction from which a train is approaching a section or sections of track in the stretch.

Another object of my invention is to provide a supplemental signaling system which gives to the operator of a special vehicle a positive indication of the direction of movement of an approaching train.

A furtherobject is to provide an improved supplemental signaling system for the operation of special wayside indicators which govern the movement of special vehicles only.

A further object of my invention is to provide an improved supplemental signaling system including means for preventing a receding train from iv ng a falseindication that a train is pproachin My invention is disclosed herein as applied to two different types of conventional block signal systems. One type of system is an absolute permissive block system controlling the movement of trains over a single track stretch having spaced passing sidings. The other type of system disclosed is a block signal system adapted for use on each track of a multiple-track railway, which block signal system controls movements over the track in one direction only. Both of the systems disclosed employ conventional direct current track circuits and supply coded alternating current to the track rails for the control of traincarried cab signaling or train control equipment of the continuous inductive type, such as is shown, for example, in Letters Patent of the United States No. 1,986,679, issued January 1, 1935, to Lloyd V. Lewis for Railway Trafiic Controlling Apparatus.

In both of the supplemental signaling systems described herein, the special vehicles are each provided with a receiving relay responsive to alternating current in the track rails which controls visual and audible indicators. The motor car carried apparatus is so arranged that a lamp is steadily lighted as long as the relay is energized by steady alternating current supplied to the track rails, thus indicating to the operator that no train is approaching from either direction. The lamp is extinguished and an audible signal is sounded when the supply of currentis interrupted.

It follows that either the absence of alternating current or the presence of alternating current interrupted at a specified rate, such as times per minute, as provided for the control of the cab signals on an approaching train constitutes a warning to the operator of a motor car that this should be removed from the track.

In the absolute permissive block signaling system disclosed herein, the indications received by the motor car operator additionally indicate the direction of approach of a train. When a'train approaches from one direction, the supply of alternating current is cut off, while the approach of a train from the opposite direction interrupts the supply of alternating current intermittently at a predetermined low rate, such as 15 times per minute, which is readily distinguishable from the cab signaling frequencies mentioned. In either case the supply of motor car indication current is out off by the shunting efiect of the wheels and axles of the train when it enters the section occupied by the motor car.

In the single direction signaling system described herein, wayside motor car indicators are provided for the control of the special railway vehicles, in addition to the indicators carried by the motor cars themselves. This supplemental signaling system utilizes line circuits extending between successive signal locations and forming part ofthe conventional block signaling system. In the'supplemental system, a-series approach relay is added at the advance or energy supply end of each of these line circuits, which controls the supply of energy from an adjacent local source to a second line circuit which extends to the next succeeding signal location in advance. This second line circuit is provided, in accordance with the invention, for the control of a neutral relay and a biased polar relay at such location. The neutral relay operates pole-changing contacts in the corresponding second line circuit extending one block further in advance, while the biased polar relay operates means for controlling an adjacent'wayside indicator and for controlling the supply of motor car indicator current to the track rails of the section through which its circuit extends. The operation is such that when a train enters a given section, it deenergizes the signal and also the series approach relay in the signal circuit at the location of the nex'tsignal in advance which opens the second line circuit extending to the location of the second signal in advance, deenergizing both the polar and neutral relays at that location. De-

energization of that neutral relay pole-changes the second line circuit of extending to the location of the third signal in advance, thereby deenergizing the polar relay at that location. Since each polar relay controls the motor car warning indication for its particular section, it will be seen that a train moving in the normal direction will indicate its approach to a motor car occupying either of the two block sections ahead of the one occupied by the approaching train.

' Although the signal system is arranged for the control'of train movements in one direction only, it is assumed that at times train movements in the opposite direction will be made. The motor car indicator system provides protection for such train movements by utilizing the signal control circuits to cut ofi the'motor car indicator current from the rails of a section in the rear of a signal which indicates cautionor stop, that is to say, from the rails of the two sections ahead of a train which is moving in the direction opposite to the normal direction. -Directional stick relays at each signal location prevent cutting off the motor car indicator current in this manner from the rails of the sections in the rear of a train moving in the normal direction.

I shall describe two signaling systems embodying my invention, and shall then point out the novel features thereof in claims.

In the drawings, Figs. 1A, 1B,'and 1C taken together constitute a' diagrammatic view of a stretch of railway track equipped with a conventlonal absolute permissive block signaling system and also with a supplemental signaling system incorporating certain features of my invention. Fig. 2 is a diagrammatic view of one form of indication equipment which may be carried on a railway'motor car or other special vehicle to'be used in cooperation with the wayside apparatus of my invention. Figs. 3A and 3B taken together form a diagrammatic view of a stretch of railway track equipped with a conventional block signaling system for single direction running and also with a modified form of supplemental signaling system embodying my invention.

Similar reference characters refer to similar parts in each of the several views.

Figs. 1A, 1B, and 10 When these three figures are placed side by side with Fig. 1B at the right of Fig. 1A and Fi 10 at the right of Fig. 13, they illustrate my invention as applied to a stretch of single track between two passing sidings PS. When Fig. 1C is placed at the left of Fig. 1A, and Fig. 13 at the right of Fig. 1A, these drawings illustrate my invention as applied to the main track stretch adjoining a passing siding and interposed between two single track stretches.

In most instances in the drawings, the relay contacts are located directly below the winding of the relay which operates them. In order to simplify the drawings, however, the relay contacts have in some cases been separated from their associated winding. In these instances the relay winding is designated by appropriate reference characters placed above the contact.

When the drawings are arranged with Fig. 13 at the right of Fig. 1A, and Fig. 10 at the right of Fig. 13, it may be seen that the stretch of single track shown extends from switch I in Fig. 1A, to switch II in Fig. 1B, and is provided with signals 3, 5, l, and 9 controlling westbound trafiic and signals 4, 6, 8, and I0 controlling eastbound traific. The rails 1a and 1b are provided with insulated rail joints by which the main track is divided into track sections IT, 4T, 5T, 6T, IT, 8T, and ST. Each section is provided with the usual normally closed track circuit including a track relay TR at one end energized by a track battery TB connected across the rails at the other end.

Circuit elements associated with a particular track section are indicated by alphabetical reference characters designating the type of element prefixed by numerical reference characters corresponding to the number of the particular sec tion. For example, 6TB indicates the track relay TR for section 6T.

Each track section is provided with two track transformers W and E. Transformer W has its secondary winding connected across the track rails at the west end of the track section and supplies cab signaling current to the track rails for the control of westbound trains. Transformer E is connected across the track rails at the east end of the track section and supplies cab signaling current to therails for the control of eastbound trains. Each transformer secondary at the battery end of a track section is connected in series with the track battery. Each transformer secondary at the relay end of a track section is connected in parallel with the track relay. A suitable current limiting impedance is connected in series with the transformer secondary winding in each instance.

When alternating current is supplied to the primary winding of a track transformer, a similar current is induced in the secondary winding and thereby suplied to the rails of the track section. The windings of the track relays present a high impedance to the alternating current, so that the alternating current flowing through the track relay windings is negligible. Hence, alternating electrical current may be supplied to a track section without affecting the operation of the direct current track circuit in that section.

The wayside signals 3, 4, 5, 6, l, 8, 9, and II] are of the well-known searchlight type and may be constructed as shown in Letters Patent of the i United States No. 1,864,224,]granted to Wesley Z.B.-'Wells on June [21,, 1932. Each signal :is illustrated .inth'e' drawing as comprising a wayside structure .shown beside the track rails and a cor- ;respondinglynumbered mechanism having a controlwinding identified by the ,suffix G and appearing in the circuit plans substantially below "the waysiderstructure. When the-windin is energized with direct current of normal polarity,

the signal gives a proceed indication by displaying a green light and a contact G is picked up. When the winding is energized with directcurrent of :reversepolarity, the signal gives a caution indication by the display-of a yellowlightand a contact ,Ygis ,pickedup. When thewindin is de- =energi-zed both the contacts Y and G are re- ..leased, and the signal gives a stopindicationby :are designated B and C, respectively. A source ofalternating current,'not shown, is also provided .2

:at each signal location, the terminals of which are designated BX and CK.

The signals 4, 5, 6, l, 8, and 9 are provided with repeater relays PC. Each of these relays is arranged to be energized when either the Yer G contact of its associated signal is picked up.

The signals's and ID are provided with repeater relays 13PC and IUPC which repeat the position of. the G contact only of the associated signal and are also provided with repeater relays 332'? and WP which repeat the position of their Y contacts.

At the battery end of track section IT, a repeating relay ITPR is provided controlled by the relay [TR at the opposite end of section IT.

The signals 5-, 6, l, 8, and 9 are provided with directional stick relays 58, 68, ES, 88, and 9S. Eachof these relays is picked up each time that a train accepts a proceed or caution signal and remains picked up until its associated signal is again restored to its proceed or caution position after the passage of a train. The pickup and stick circuits 'for these relays are conventional and referring to stick relay 58, it may be ses-n that its pickup circuit extends from positive bat tery terminal B over a back contact of relay 5TB, over a front contact of relay SP0, and through the winding of relay ES to negative battery terminal C. When signal 5 indicates :proceed or caution, relay EPC .is energized "and its front contact is closed. If a westbound train accepts this signal, it deenergizes relay 5TB upon its entry into section 5T. The front contacts of relay 5P0 remain closed for a short time after the winding of signal 5 is deenergized by the opening of thefrontcontacts of relay 5TB. The length of time the front contacts of relay 5P0 remain closed under these conditions is determined by the drop-out time of the contacts Y and G of signal 5 and of relay 5P0. In any event, the pickup circuit for stick relay 5S is closed during this interval. As soon as the wind ing of relay 5s is energized, it closes its front contact, completing a stick circuit which may be traced from the positive terminal B through a back contact of relay 5P0, and the front contact of stick relay 58, the winding of relay 55 to the negative battery terminal C. This stick circuit remains energized until relay SP0 is againener- :gizedand opens its backcon-tac't.

r 'The signals .3 and in are also provided with directional stick relays 3S and IEIS, the pickup and stick circuits for which are somewhat different from the circuits of the otherstick relays .just described. This difference is occasioned by the fact that the relays .EPC and lzliPC repeat only the proceed positions of the signals '3 and I0, whereas the PC relays for the other signals repeat both the proceed and caution positions.

The pickup circuit for stick relay HIS may be traced from positive battery terminal vB through a back contact or relay I'TR, thence throughifront contacts of relays MPG and :IBYP in parallel to thewindingof :relay HIS-and thence tonegative battery terminal 0. This circuit is completed through the front contact :of relay .HIPC whenevertaltrain accepts asi'gnal l 0 at proceed. When a train accepts signal Iii iat'caution, the pickup circuitis completed through the frontc'ontact of relay IJJYP. .As soon as relay I 0S picks up, it completes a stick circuit which may be traced from the positive battery terminal .Bthrough a back contact of relay lflPC and the front contact of relay 1 ES to the windingof relay HIS and thence to the negative battery terminal C. This stick circuit remains energized until relay MP0 is again energized, which occurs when signal H1 is again moved to its proceed position.

At each signal location there are located one or more code transmitting relays for ca-b signal purposes which are indicated by the reference characters IBBCT in the drawings. This reference character indicates that the code transmitting relay opens and closes its contacts 180 times per minute. There are also provided at the several signal locations other code transmitting relays for use in the supplemental signaling system for motor cars, which are identified by the reference character [501 in the drawings, indicating that they open and close their contacts 15 times per minute. These frequencies are chosen by way of example only, and other suitable frequencies may be used, provided they are sufilciently far apart to be readily distinguishable by the code responsive apparatus.

The several signals are energized by circuits which are generally conventional in an absolute permissive block type of signaling system. The particular circuits described are shown by way of example only, and other equivalent circuits may be readily used in carrying out my invention. The circuits for the single track stretch are arranged so that all signals normally indicate proceed, and each signal governing trafiic in one direction is set to stop whenever a train approaching from the opposite direction enters the stretch. Also, when a train accepts a signal governing its movement, thesignal is put to stop and continues to indicate stop as long as the train occupies the first block section immediately in advance of the signal. When the train vacates the first block section in advance, the signal indicates caution, and when the train vacates the second block section in advance, the signal indicates proceed.

The circuits for the signals which govern east- :bound traffic movements through the single track stretch shown in Figs. 1A, 1B and 10 will now be traced in detail. Vflien the track sections BT and GT are unoccupied, the winding &G for signal 8, Fig. 1B, is energized 'over a circuit including a front contact of the track relay BTR, a back contact of the directional "stick relay 18, line wires 3| and 32, a front contact of the track relay 9TB, and extending to terminals B- and C over pole-changer contacts of relay IOPC. Relay IllPC is picked u to supply current of normal polarity to this circuit to cause signal 8 to indicate proceed only when signal indicates proceed, and the polarity is reversed to cause signal 8 to indicate caution when signal ID indicates caution or stop. Relay 8P0 picks up when Winding 8G is energized, and if sections IT and ST are unoccupied, energizes winding 6G over a circuit including a front contact of relay BTR, a back contact of relay S, line wires 33 and 34, and extending to terminals B and C over the front contacts of relays ITR. and 8P0. Relay SPC when picked up supplies current of normal polarity to this circuit to cause signal 5 to indicate proceed when signal 8 indicates proceed or caution. When relay 8P0 is released due to the occupancy of section 8T or 9T by an eastbound train, relay BS is picked up and connects terminal B over a back contact of relay 8P0 to the circuit for winding 6G so that this winding is energized by current of reverse polarity to cause signal 5 to indicate caution.

When winding 6G is energized, relay EPC picks up and if sections 5T and 4T are unoccupied, winding 4G is energized by current of normal polarity over a circuit including a front contact of relay ATR, line wires l3 and I5, and extending to terminals B and C over the front contacts of relays 5TB and SP0, so that signal 4 indicates proceed when signal 6 indicates proceed or caution. When relay BPC is released due to the occupancy of section GT or IT by an eastbound train, relay (is is picked up and connects terminal B to this circuit so that current of reverse polarity is supplied to winding 4G to cause signal 4 to indicate caution.

Considering now the siding area, and placing Fig. 10 at the left of Fig. 1A; it will be seen that when the track sections IT and AT are unoccupied, winding IUG is energized over a circuit including a, front contact of relay ITR, line wires 35 and 36, a front contact of relay 4TB, and extending to terminals B and C at the polechanger contacts of relay iPC, which relay is picked up to supply current of normal polarity to the circuit to cause signal It] to indicate proceed when Winding 4G is energized to cause signal t to indicate caution or proceed, and supplies current of reverse polarity to cause signal It to indicate caution, when signal 4 indicates stop.

The circuits for governing Westbound traffic movements are similar, that is to say, the circuits for controlling signals 9, I, 5 and 3 correspond respectively to those for signals 4, 6, 8 and If! just traced, and therefore will not be traced in detail.

As previously mentioned, coded cab signal current is supplied to the rails of the several track sections through transformers W or E located at the ends of their respective track sections. In the particular arrangement disclosed herein, the cab signal current is alternating current interrupted at a frequency of 180 times per minute, the train carried apparatus of the Lewis patent referred to being responsive to coded current of this frequency in the rails ahead of the train to cause the display of a proceed indication in the cab of the leading vehicle of the train. This train governing current is supplied to the rails of a given track section only when the signal immediately in advance of the section indicates proceed, and in certain cases it is supplied to the rails of a section only when such section is occupied by a train.

The supplemental signalin system for the control of the motor car indication apparatus of Fig. 2 normally supplies steady alternating current to the rails of each section for indicating to the operator of a motor car at any point in the stretch that no train is approaching within a predetermined distancefrom either direction. The direction from which a train is approaching is indicated by cutting off the supply of alternating current from one or more sections in front of a westbound train, and by interrupting the supply of alternating current supplied to one or more sections in front of an eastbound train at a code rate of 15 times per minute.

Normally, steady alternating current is supplied to the rails of section iT by transformer 4W which is energized over the circuit from terminal CX through its primary winding, front contact a of relay QTR. and front contacts of relays 4P0 and 31C to terminal BX. Steady alternating current is normally supplied to the rails of sections ET and 6T by transformers 5E and SW which are energized over circuits including the line wires 31 and 38, front contacts a of the track relays 5TB, and 6TH, respectively, and extending over front contacts of relays 61 C and SP0 in series to terminal BX. Section ET is also normally supplied with code current by transformer 5W but this is without effect upon the motor car apparatus when steady current is sup plied to the same section. The circuit for transformer 5W extends to terminal BX over front contact I) of relay iTR, a front contact of relay SP0 and a contact of a code transmitter IBBCT.

Steady alternating current is normally supplied to the rails of sections IT and ST by transformers TE and SW, which are energized over circuits including the line wires 38 and 43, front contacts a of relays lTR and 8TB, respectively, and extending over front contacts of relays SP0 and 'iPC in series to terminal BX. Section IT is also normally supplied with 180 code current by transformer 1W which is energized over line wire 4|, front contact I) of relay 6TB, and front contacts of relay SP0 and of the adjacent code transmitter IBGCT.

Steady alternating current is normally supplied to the rails of sections 9'1 and IT by transformers 9E and IW, which are energized over front contacts a of relays 9TB and lTR, respectively, a back contact of relay HIS, and front contacts of relays MPG and QPC. Section ST is also supplied with 180 code current by transformer 9W, the circuit for which includes front contact b of relay 8TB, a front contact of relay 'IPC and a contact of a code transmitter I 800T.

The effect of the passage of a train through the stretch of track shown in Figs. 1A, 1B and 10 will now be explained in detail.

It will be assumed first that an eastbound train is occupying section iT. Windings IOG and 3G are deenergized, due to the release of relay ITR by the train so that signals H3 and 3 indicate stop and relays lfiPC and 3P0 are released, causing signal 8 at the left and signal 5 at the right to indicate caution, while all of the other signals indicate proceed. The track repeater relay ITPR is released, causing transformer IE to supply coded cab signal current to the rails of section IT in front of the train to correspond with the proceed indication displayed by signal 3. The primary circuit for transformer 5E is now closed from terminal CX through its winding to terminal BX over back contacts of relays I TPR, 3PC, 3YP, a

front; contact of relay 412C. and a, periodically op Transformers. 5E, 6W, 7E1; 8W tc.- onti ueitc pp y. steady alternating. cu re t. to. he. rels i? their respective s ctions; in fif. i.i....c the tree. well as to the similar sections behind the tra If the train. en ered section. .l from seetioiitfli' r lay lTR is h ldin re ay Hi5. oi frontcontact of relay 95 rid s ntact of r lay 153C i the. i former 95. so t at steady a te natin cu supplied to he ra ls of: se tion 9.1 other... transformer leenersizeli. a .8 code supp ied to. se t on 9T. y tr ilsf to. ons derin for he moment. tha sectio II is. West o nd, it. w l be sec-c that... t 180 code. c r ent. upp ed by rentio mer provided as a mo o c r Warn n n and h t. ormer. W- is supp in 80v 0 r-eat S nal, contro t t e rail o se ion IT; n.

front th s t a n to co resp nd wi h the roc ed indic tion f si nal. F rt ermore, t th west: nd rai en e ed ection lT om sectio 9T r y s i ke p to cau e tran fo mer. 4W to supply stead alternati urrent to th it ct on 4.1 in e o he Wes nd e p e o 15 c de.-

u n n ow o a. considerat on o the c stbound a n when it en e sec on. 41 the r lease f re a 4 H ce ne e tee ndi Mi e ou si na 4 t Stop, si g relay 4P a a o deenergizing in cascade thewindings and relays PC f t po in s nal a 9 a a of the train so that these signals indicatest'oli the release of relay SEC causing the indications of signals 3 and 5 tq change from proceed to caution, and when the eastbound train yacates section IT, signal 3 in the rear indicates proceed nd. si n l i t e. r ar dic tes c ut onransf crme @E i er iz d soon a the r in terssectio itT to. su pl c ded cab s a co ntto the rails in r nt. of th train ove be k contact of re ay fl t ont contact 21 o r a T-1t,..f.r nt c n act o r y SP6. and. ontact of co e. tr ns itt r tlicT.

n front. o the rain he release of relay 5- C nnec s. W e 7 nd .8. t rminal BX ve a contact of a code transmitter I 501 so that trans formers 5E and 6W supply current interrupted at the code a e t i ns 5 d B nd also open t e circ it over r 4| r t ansf me 1W. The release of relay lPC similarly energizes transformer 1E and 8W over wires 39 and 4,0, to supply 15 code to the rails of sections IT and BI, and opens the circuit for transformer 9W, while the release of relays 91C and 3P9 causes transformers 915., l W and 4W to supply 1,5 code to therails of sections 9T, IT and AT.

It will b see t erefore, that when the. caste bonnd train enters section 41, the limit of the motor car warning territory is extended from the end of this section to the end of the corresponding section 4T of the next block in advance.

The release of the track relays as the train advances through sections 4T to 9'1 causes alternailing current interrupted at the 1.80 code rate former 3E over back contact'fc ofrelayllTRffront contact 17 of relay 9TB, and a contact of relay NBC; and traneiorme 9E1; over,- back contactc of relay 9T3 and a. front contactot relay L92 for si nal IS. in from. of h ra n ignal Ill in. the. rear thetnainstano e at; caution and its relay .Iil nel a.sed,a d.if re:- l y Ills isenereized, lsconnected: over front. contact oi relay When. the east oundtr in Qccllp si nal 6, is no torsion by the ener izin re ay and. rel asin relay. lay 65. opens its acl; contac lathe winding tqto mainta n signala st si n relay 4 0; rear to indicate pro. ed. Bel y l l pi a d r lea es .ela HLSJ. so ndicatcspr ceed hen. the. eas -hound t si nal. i simila lt r. 11 5 i i-"l e m the tra k. nally wh n the ra n ccete l stemio t e s n e track tr sumes i s. eormai c ine is. ter le. Since the s s-realv system. s. two direc ions, the effe t eta W movement is s ilar to t he'c ntr l. oi th waysid a. t t s na s b dllrersin hatthe mo orcar'waniin oi ll 1 preach of a westbound tra nis pr d i e on the supply of s dy al ernating m. the ra ls When t e wes holinlitrain .oec oiess cti n for example, the su p y .ofic r ent t formers SW and t i oii becausere cy e e nst ad ne r: 'IPC; from. transio me e. end because. sere ar cent signals. Alternating current flowing in the track rails which is coded or interrupted at a relatively slow rate, such as 15 times per minute, indicates that an eastbound train is approaching the section within the control limits of the signals. The absence of alternating current in the track circuits or the presence of alternating current which is coded or interrupted at the rate of 1 80 times per minute indicates either that a westbound train is approaching, or that a train is in the same track section, or in some cases, in an immediately adjacent track section.

Fig. 2

Referring now to Fig. 2, a diagrammatic view of one arrangement of indication apparatus is there shown which may be employed on motor cars or other special vehicles which are operated over the stretch of track described above. As indicated diagrammatically in Fig. 2, the wheels WI and W2 are insulated from the frame of the vehicle and from each other by interpcsing insulated bushings and washers 2 between the wheelsand the axle AX. It is to be understood that the other pair of wheels, not shown, on the motor car are similarly insulated, so that the car will not shunt a track circuit. A slip ring SRI is electrically connected with the wheel WI and a second slip ring SR2 is electrically connected with the wheel W2. Connected in series between the slip rings SRI and SR2 are the condenser IQ and the primary winding of a transformer ITT. The secondary Winding of the transformer ITT is connected to the input terminals of a bridge-type rectifier IRX, and the winding of'an indicator relay IR is connected across the output terminals of this rectifier. It will be apparent that when the car moves over the rails of a track section the condenser IQ will block the flow of direct current track circuit energy, but will permit the flow of alternating current from one track rail to the other through the primary winding of the transformer ITT. The alternating current induced in the secondary winding of transformer ITT is rectified by rectifier IRX, and is supplied to the winding of relay IR, and as a result, relay IR picks up to establish a circuit, obvious from the drawing, for supplying energy over its front contact from the battery IE to light the indicator lamp KE. If the supply of alternating current to the rails R is interrupted, current is no longer supplied to the winding of relay IR and its contacts release, extinguishing the lamp KE, and establishing a circuit for supplying energy to a warning bell KS. A switch SW is shown in series with the circuit for supplying energy to the indication lamp KE and the warning bell KS, so that the equipment may be deenergized when the car is removed from the rails.

It is to be understood that my invention is not limited to the specific arrangement of vehiclecarried indicator equipment shown in Fig. 2, and any suitable indicator means may be employed which will detect a distinctive indicating current supplied to the track rails and distinguish that current from the current used to energize the track relays. When alternating current is employed, as shown herein, the relay IR may be made responsive to current flowing in the track rails by the provision of receiving coils on the motor car in inductive relation to the rails, together with an amplifier for amplifying the energy induced in such coils, such an arrangement being well known from its use for the con- 12 trol of train-carried cab signals, as shown in the Lewis Patent No. 1,986,679 hereinbefore referred to.

It will be seen that if a car equipped with apparatus as shown in Fig. 2 travels over the stretch of track shown in Figs. 1A and 1B at a time when the system is in its normal condition with all of the track relays picked up, each of the track sections will in turn supply steady alternating current to the apparatus on the car and the relay IR on the car will remain energized, thus causing the lamp KE to remain lighted, and thereby indicate to the operator of the motor car that he may safely continue running.

It will be readily apparent, however, that the system of my invention differs very materially from the conventional cab signaling systems for the continuous control of train movements by apparatus responsive to alternating current in the track rails. In such systems, the track relay for the occupied section is shunted by the wheels and axles of the train, which complete a path for the cab signaling current from rail to rail in front of the train and this current is supplied to the rails at one end of the section or the other depending upon the trafiic direction established. The motor car indication current on the other hand is supplied at one end only at each section for either direction of motor car operation, and its circuit is effectively completed from rail to rail in the manner indicated in Fig. 2 only in the absence of a train shunt. That is to say, the motor car current is supplied to the rails of a section over a circuit governed by the front contacts of the track relay for the section at a time when cab signaling current is not needed. It follows that a cab signaling system which embodies the approach control principle in which "the control current is supplied to the rails of a section in response to the release of the track relay may be used in conjunction with my motor car indicator system without interference, merely by a choice of currents of different char- "acteristics for the two systems.

Figs. 3A and 3B In Figs. 3A and 313 a stretch of railway track is shown to which is applied a modified form of my supplemental signaling system for special vehicles. This stretch of track represents one track of a double-track railway, which is equipped with conventional wayside signals for single direction running only and also with cab signals for single direction running. The supplemental signaling system illustrated in these figures warns operators of motor cars of trains approaching from either direction, but does not inform the motor car operator as to the direction of approach.

The Figures 3A and 3B may be placed end to end either with Fig. 33 at the right of Fig. 3A or with Fig. 33 at the left of Fig. 3A.

The stretch of track shown in these figures is divided into sections IZT, MT, I6T, and I8T, located immediately in advance of signals I2, I4,

l6, and I8, respectively.

The motor car indication system of Figs. 3A and 3B not only governs the indicators carried on the cars, but also governs wayside indicators IZMC, MMC, IBMC, and IBMC. These Wayside indicators may be, for example, of the type shown and claimed in the copending application of Arthur W. Fisher and Wesley B. Wells, Serial No. 17,436, filed March 27, 1948, for Indicators.

The normal direction of traffic movement on the stretch of railway track shown in Figs. 3A and 3B is eastbound, or from left to right in the drawings, as indicated by the arrows. The signals l2, M, It, and I8 control eastbound trailic only, no, wayside signals being provided for westbound traffic.

The signals l2, M, 6, and I8 are conventional color light signals having green, yellow and .red

lamps G, Y and R haying lighting circuits which are governed in the manner shown for signal 12. When the, track relay, such as relay IZTR for the section directly in advanceof the signal, is released, its lamp 1?. is lighted to indicatestop. When this track relay is energized, lamp Y is lighted to indicatecaution provided anassociated linev relay ,IZDR is released, and lamp G is lighted in place of lamp Y to indicate proceed when the line relay is energized. Each line relay DR is controlled over a line circuit governed by the track relays for two sections in advance, as i1- lustrated by the circuit for relay IZDR, which may be :traced from positive battery terminal 13 at the location of signal Id through the winding ofa series approach relay MXR, over front C011? tact b of the track relay ll lTR, line wire l1, front contact 0f thetrack relay IZTR, the winding of relaylZDR, and thence Over a common return linc;wire CL to the negative battery terminal C at the location of signal I4.

The relays have been included in the signal line circuits for the purposes of myimproved motor car indication control system, and control a second series of line circuits.

Each line circuit of this second series includes atits left-hand end, a source of current, polechanging, contacts of a line relay YRand a front contact of the adjacent approach relay XR, and at its right-hand end includes the windings of an indication control relay ZR and of the polechanger relay YR. Each relay ZR is of the biased polar type responsive to ener y of one polarity only and picks up only when the controlling relays XR. and. YR. are both energized. The relays YR are ordinary neutral relays and are repeaters of the controlling relays XR, and each is connected to its line circuit through a rectifier 2D to prevent its momentary release during a reversal of the polarity of the line current by the line relay YR, which governs that circuit.

The line circuit of the second series extending between the locations of signals 12 and it may be traced from positive battery terminal B at the location of signal I2 over a front contact a of relay IZYR, line wire 19, front contact b of relay MDR, front contact 0! of relay l iTR, through the Winding of relay l lZR, rectifier 2i) and the winding of neutral relay MYR, line wire 2 l a front contact of relay I2XR, and front contact b of relay IZYR to negative battery terminal C at the location of signal 12. When relay IZYR is deenergized, the polarity of the energy supplied to the line circuit just traced is reversed, in which case relay l iYR remains picked up, since due to the rectifier 2c the direction of current through its winding remains unchanged, while relay MZR assumes its released position due to the fact that it is responsive to current of normal polarity only.

A branch circuit is provided for at times shunting the front contact I) of relay MDR and the front contact d of relay IGTR in the line circuit under discussion. This branch circuit may be traced from line wire 19 over a front contact a of a directional stick relay MS to the right-hand terminal of the winding of relay I 4ZR.

The contact b of relay MDR and contact d of relay [4TB are provided in order .to deenergize relay MZR by an eastbound train moving in the,

normal direction and receding from the location of signal I4.

The circuits for the directional stick relays S are conventional. The pickup circuit for relay MS may be traced from the positive battery terminal B. at location [4 over back contact 6. of track relay M'IR, front contact c of relay MD and thence through winding of relay MS to neg.- ative battery terminal C. The stick circuit of relay [as may be traced from the same positive battery terminal 13 through either back contact e of relay HlTR or back contact 0 of relay MDR, and thence through front contact I of stick TBS lay 15S, and the winding of relay MS to negative battery terminal C The pickup circuit for relay its is closed whenever a train moving from left to right passes signal I l. The stick circuit for relay Ids is then completed through its front contact b and remains completed until relay MDR again picks up upon the departure of the. train from sections MT and WT. The stickrelaygl ls therefore holds its contact a closed as long as contact c of relay I 4BR is maintained open by.

deenergization of relay MDR.

The wayside motor car indicator IEMC. is en: ergized over the line wires l9 and 2! through an obvious circuit which includes a frontcontact a of relay MZR.

The relay MZR also controls a contact bswhich selectively supplies the primary winding of a track transformer l2TT with steady alternating electrical current for motor car indication purposes when the relay lZR is energized or with coded alternating electrical current for cab Signal,

purposes when the relay l-lZR is deenergized.

The circuit for supplying steady alternating current for motor car indication purposes to transformer lZTT may be traced from terminal BX of the local alternating current supply through front contact b of relay HlZR, and pri-: mary winding of transformer |2TT to terminal CX of the alternating current supply.

The circuit for supplying coded cab signal current to transformer Winding IZTT may be traced from another terminal BX cf the alternating current supply over a contact of a code trans mitter iEOCT, a front contact 1 of track relay him, back contact I) of relay MZR, and the primary winding of transformer i2T'I to terminal CX of the alternating current supply.

The secondary Winding of transformer iZTT is connected in series with the track battery [2TB and the usual current limiting impedanc across the rails of section I2T at its exit end.

Operation of Figs. 3A and 33 Let it be assumed that a train proceeding in the normal eastbound direction of trafiic is proceeding through the track stretch with the signals ahead indicating proceed, and is just entering the track section IZT. The conventional wayside signal system operates in the usual manner, and a detailed discussion of it is believed to be unnecessary here. Briefly, occupancy of any track section by a train deenergizes its track relay and sets the signal at its entrance end to stop. Deenergization of the track relay also opens the line circuit to the DR relay for thenextsig-nal in the rear, so that that signal is set to its caution position. The second and following signals in the rear of the occupied section will then indicate proceed.

When the train enters section I2T, relay I2TR releases to cause the display of a stop indication by signal 12, and opens its front contact 0 in the line circuit for relay IZDR which includes wires I7 and CL and the winding of relay MXR at th next signal location in advance. Relay NXR releases, opening its contact in the line circuit extending over line wires 22 and 23 to the location of signal i6, which is the second signal in ad- Vance of the occupied track section. Relays IBZR and ISYR therefore release, but since relays MTR and IBTR are picked up, relay ItXR is energized in series with relay l iDR over line wires 24 and CL and completes the line circuit which includes wires 25 and 26. Since relay ISYR is released, its pole-changing contacts a. and 1) supply current of reverse polarity to this line circuit which extends to location of signal [8, the third signal in advance of the occupied track section. Current of reverse polarity flowing in this circuit causes the biased polar relay ifiZR to release, but maintains relay IBYR energized. Relay IBXR is energized in series with relay ISDR over line wires 2'! and CL, allowing relay ISYR to supply current of normal polarity over line wires 28 and 29 to the location of the fourth signal in advance of the occupied section to energize relays corresponding to relays l2YR and I2ZR at that location, the relay corresponding to relay IZXR at the fourth location being energized in series with relay l8DR over line wire 35.

The release of relay l8ZR opens the energizing circuit for motor car indicator ISMC at its contact a and its contact b inserts a contact of a code transmitter ISOCT in the circuit for the primary winding of transformer IGTT, so that coded alternating current for cab signal control is sup-plied to the rails of section HST in place of steady alternating current for motor car indication control.

Since at this time relay 62R is deenergized, as above described, its motor car wayside indicator IGMC is set to stop and its contact I) operates to discontinue the supply of steady alternating current to transformer MTT and substitutes the coded cab signal current.

The energizing circuit for relay lZR is opened at the front contact of relay I2XR, which relay was released by the track relay for the section in the rear of section I'ZT and is now held deenergized by the opening of front contact I) of relay IZTR. Consequently, wayside motor car indicator MMC is also set to stop, and the motor car indication current is removed from transformer lZTT' and replaced by the coded cab signal current.

When the train above referred to entered section IZT, stick relay 12S picked up and its contact a bridges contact I) of relay IZDR and contact d of relay IZTR in the energizing circuit for relays IZYR and I2ZR which includes line wires 28 and 29 and is held open by relay IBXR for section [8T in the rear of section l2T, relay IBXR being held released by the track relay IBTR until the train vacates that section. If there is no second train following the one in section IZT to maintain relay IBXR released, relays I2YR and IZZR then become energized. Under this condition relay IZZR will cause indicator IZMC to display a clear indication as soon as the train vacates the section in the rear, and will cause steady alternating current to be supplied through 16 transformer I8TT over front contact b of relay IZZR to the rails of the section in the rear of the one occupied by the receding train.

When the train enters section IGT, relay MTR releases and causes the indication of signal It to change from proceed to stop. The opening of contact I of relay l lTR cuts 01f the supply of coded current to the rails of section I2T, and relay MS picks up over back contact e of relay l lTR. In addition, the opening of contact c of relay MTR releases relays I4DR and ISXR, and relay IGXR deenergizes relays IBYR and I8ZR, the latter relay being already in its released position. Relay I8YR reverses the polarity of the current supplied over line wires 28 and 29 to the relays IZYR andl2ZR at the next location in advance, and this relay IZZR releases to display a warning indication by the release of its indicator IZMC and to supply coded cab signal current in place of steady current to the rails of its section.

When the train vacates the rear section I2T, its track relay 12TH picks up to cause the indication of its signal 12 to change from stop to caution. Relays l2DR and l iXR are held released by the opening of contact b of relay l lTR, and relay l2S is held energized over back contact 0 of relay IZDR. If there is no following train within its control limits, relay lZXR picks up over contact I) of relay l2TR, and if relay IZYR is also energized, relays MYR and l lZR pick up over contact a of relay MS. Relay MZR then energizes indicator MMC and supplies steady alternating current to the rails of section IZT.

When the train advances into section I6T, the indication of signal iii changes from proceed to stop, the supply of coded current to section MT is out 01f, relay ISS picks up, and relays IGDR and laXR release, clue to the release of relay IBTR. In front of the train, relay IBXR deenergizes relays iZYR and |2ZR at the next location in advance and relay IZYR releases relay MZR to extend the motor car warning limit to include the second location in advance.

When the train in section i6T vacates the rear section MT, its track relay I iTR picks up to cause the indication of signal [4 to change from stop to caution, and to reenergiz relays IZDR and l lXR. Relay l2DR causes the indication of the rear signal [2 to change from caution to proceed, and releases relay 128. If there is no train following the one in section IBT, relays I2YR and i2ZR in the rear are maintained energized over contact d of relay I2DR and contact b of relay I2TR, and relays MYR and MZR are energized over contact a of relay MS. Relays IGYR and IBZR pick up, due to the energization of relay MXR, and relay ISZR energizes indicator IGMC and supplies steady alternating current to the rails of section MT.

From the foregoing, it may be seen that an eastbound train occupying a track section deenergizes the wayside motor car indicators at the three signal locations in advance of the occupied section, and causes the supply of steady alternating electrical current, the presence of which indicates to a motor car operator that no train is approaching, to be cut off from the rails of the section occupied by the train and from the rails of the two sections in advance, and also causes coded alternating current for cab signal 1purposes to be supplied to the rails of these secions.

Consider now the conditions which occur when a train is moving westbound, opposite to the nor- 11- mal' direction. of' trafiic through, the stretch oftrack shown in: the drawings; Letit be assumed that a. westbound. train is entering section IGT. The shunting efiect of its wheels and axles prevents. transformer |6TT from supplying current to. the. rails of that portion of; section itT which isinfront of. the train, and also deenergizestraclr relay IETR, which opens its contact at in the cir-- gizing circuit of relay MZR. Wayside motor car indicator M'MC is therefore also set to stop, and

the supply of current to track transformer IZTI' is changedv from steady tov coded alternating current;

It'may therefore. be. seen. that a westbound train deenergizes the wayside motor car indicators at two locations. in advance and removes. the motor, car indication current from two track-sections in advance.

It will also be seen that for either direction of train movement, whena train enters a block section the zone of motor car protection is extended toinclude; three full. sections in advance, of the train, this zone decreasing to two sections as the train approaches the exit end of the section through which it is moving.

Although I have shown in this system the use of both wayside motor car indicators, such as those indicated at MC in the drawings, and carcarried indicators such as illustrated in Fig. 2, it should be understood that either one of these may be used to the exclusion of the other, if desired.

The cab signal system illustrated herein gives to the engineman an indication of the condition of the next track section in advance, as to whether or not it is occupied. For example, the

supply of cab signal energy to transformer IZ'IT is controlled by front contact j of relay 14TH. Accordingly, the cab signal energy is'supplied to the rails of section EZT only if section MT is unoccupied. The back contacts 3) of the ZR relays in this system provide approach control for the cab signals, and it will be seen that the cab signal current is supplied to the rails of a given section only when a train is within or approaching that section.

Although I have herein shown and described only two signaling systems embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Eaving' thus described my invention, what I claim is: H

1. In combination with a stretch of railway track. divided into a plurality of sections'each having a track relay which is normally energized by current supplied to the rails of its section and which releases due to the shunting effect of the wheels and axles when a train occupies its section, said stretch being provided with a railway signaling system controlled by said track relays for governing the movement of trains through said a supplementary signaling system for the prctection of specialvehicles in said. stretch which are not adapted to shunt .said track relays, com- 1e prising indication means on each special vehicle selectively responsive to indication current in the track rails of one character or another different from that normally supplied to said track relays, and indication current supply means controlled by said track relays andefiective to supply indi cation current of said one character to the railsv of each section only when that section is unoccupied, said means being further effective to cut off said indication current when a train approaches the section from one direction and to supply indication current of the other characterwhen and only when a train approaches the section from" the opposite direction.

2.. In combination with astretch ofrailway track arranged for the operation of trains each equipped with train-carried signaling apparatus: including-a receivcr responsive to certain periodie Cally interrupted alternating currents flowing in.

the track rails, said' stretch of track being die vided into sections. each having atrack; relay which is normally energized by direct current. supplied through the rails of its section and which releases due to the-shunting efiect of thewheels and axles when a train occupies its section, a Sig-- naling system for the protection of special ve hicles in said stretch which, are not. adapted to; shunt said track relays, comprising indication means. on said special vehicles responsive to alternating current in the track rails, indication. controlling meansrfor each section controlled bythetrack relays of a plurality of said sections, a first source of periodically interrupted alternat ingcurrent of a type to which said train-carried receivers are responsive, a second source-ofperiodically interrupted alternating current of a; dis, tinctively different type-towhich said special ve.-. hiclereceivers are responsive, a source of steadyalternating current, and contacts operated by each said indication controlling means effective to connect said first source to the track rails of its section whenever such section is occupied by a; train, to connect said second source to the rails of such section only when a train is approach-- ing said section within a predetermined distance in one direction, to disconnect allsaid sources: from the rails ofsuchsection when a train-isyape proaching within a predetermined distance-in the opposite direction, and toconnect said source.- ofv steady alternating currentto the rails: of. such section onlywhen said section isunoccupied by-a train and no train is approaching within a pre-- determined distance in either direction.

3. In combination with a stretch of railwaytrack divided into aplu-rality of sections each having a track relay which is normally energized by direct current supplied to the rails of its section and which releases due to the shunting effect of the wheels and axles when a train occupies its section, said stretch being provided with a. railway signaling system controllled by said track relays for governing the movement of trains through said stretch, said signaling system including two sets of signals for controlling traflic in opposite directions and corresponding sets of contacts movable substantially concurrently with 19 section controlled by a contact of one of said sets of contacts for disconnecting both of said sources from the rails of said section when a train is approaching from one direction and for permitting connection of said sources to the rails at other times; and second circuit means for each section controlled by a contact of the other set of contacts and eiTective when said first circuit means permits connection of the sources to the rails to connect said first source to the rail when no train is approaching and to connect said second source to the rails when a train is approaching from the opposite direction.

4. In combination with a stretch of railway track arranged for the operation of trains each equipped with train-carried signaling apparatus including a receiver responsive to coded alternating currents flowing in the track rails, said stretch of tracl; being divided into a plurality of sections each having a track relay which is normally energized by direct current supplied to the rails of its section and which releases due to the shunting efiect of the wheels and axles when a train occupies its section, said stretch being provided with a wayside block signaling system controlled by said track relays for governingthe movement of trains through said stretch, said signaling system including two sets of signals for controlling trafiic in opposite directions and corresponding sets of electric contacts movable substantially concurrently with said signals to open and close circuits corresponding to the signal indications; a supplementary signaling system for the protection of special vehicles in said stretch which are not adapted to shunt said track relay, comprising indication means on each special vehicle responsive to alternating current in the track rails: a first source of current adapted to supply steady alternating current to the rails of the section, a second source of current adapted to supply coded alternating current to the rails of the section to which said traincarried apparatus is nonresponsive, a third source of current adapted to supply differently coded alternating current to said rails of a type to which said train-carried apparatus is selectively responsive, a first circuit means for each section including the track relay thereof and effective when the section is occupied to connect only, said third source to the rails, and means controlled jointly by the sets of contacts associated with signals for governing traffic in opposite directions and effective only when said track relay is energized to connect said first source to the rails of the section when no train is approaching within a predetermined distance in either direction, to connect said second source to the rails when a train is approaching within said distance in one direction, and to disconnect both said first and second source from the rails when a train is approaching within said distance in the opposite direction.

5. In combination with a stretch of railway track divided into a plurality of sections each having a track relay which is normally energized by direct current supplied to the rails of its section and which releases due to the shunting effect of the wheels and axles when a train occupies its section, said stretch being provided with a railway signaling system controlled by said track relays for governing the movement of trains through said stretch, said signaling system including two sets of signals for controlling traflic in opposite directions and corresponding sets of contacts movable substantially concurrently with operation of said signals to open and close electric circuits corresponding to the signal indications; a supplementary signaling system for the protection of special vehicles in said stretch which are not adapted to shunt said track relays, comprising indication means on each special vehicle responsive to alternating current in the track rails; a source of steady alternating current, a source of coded alternating current, means for each section controlled jointly by the sets of contacts for the signals controlling trafiic in opposite directions for connecting said first source to the rails of said section when no train is approaching said section within a predetermined distance, for disconnecting both of said sources from the rails when a train approaches within said distance in one direction, and for disconnecting said first source and connecting said second source to the rails when a train is approaching said section and is within a predetermined distance in the opposite direction, and directionally controlled means for connecting said first source to the rails behind a receding train until said contacts are again operated in response to train movements in said stretch to provide a different connection.

6. In combination with a stretch of railway track divided into a plurality of sections each having a track relay which is normally energized. by current supplied to the rails. of itssection and which releases due to the shunting effect of the wheels and axles when a train occupies its section, said stretch being provided with a railway signaling system controlled by said track relays for governing the movement of trains through said stretch, a supplementary signaling system for the protection of special vehicles in said stretch which are not adapted to shunt said track relays, comprising indication means on each special vehicle selectively responsive to indication current in the track rails of one character or another different from that normally supplied to said track relays, and indication current supply means controlled by said track relays and effective to supply indication current of said one character to the rails of each section only when that section is unoccupied, said means being further effective to out off said indication current in each section occupied by a train and in at least one section immediately in advance of any section occupied by a train moving in one direction and to supply indication current of the other character to at least one section immediately in advance of any section occupied by a train moving in the opposite direction.

'7. In combination with a stretch of railway track divided into a plurality of sections each having a track relay which is normally energized by current supplied to the rails of its section and which releases due to the shunting eifect oi the wheels and axles when a train occupies its section, said stretch being provided with a railway signaling system controlled by said track relays for governing the movement of trains through said stretch, a supplementary signaling system for the protection of special vehicles in said stretch which are not adapted to shunt said track relays, comprising indication means on each special vehicle selectively responsive to indication current in the track rails of one character or another difierent from that normally supplied to said track relays, and indication current supply means controlled by said track relays and effective to supply indication current of said one character to the rails of each section only when that 21 section is unoccupied, said means being further effective to cut off said indication current from the rails of each section occupied by a train and from the rails of a plurality of sections in advance of a train moving in one direction and to supply indication current of the other character to the rails of a plurality of sections in advance of a train moving in the opposite direction.

HOWARD A. THOMPSON.

REFERENCES CITED The following references are of record in the file of this patent:

Number 22 UNITED STATES PATENTS Name Date Howard Apr. 12, 1927 Smith Aug. 3, 1943 Talbert et a1 Nov. 27, 1945 Judge Nov. 5, 1946 

